Melting and casting of metals



N. D. s. ROBERTSON Er Ar. 86

MELTING AND CASTING OF METALS Feb. 25, "1941.

2 Sheets-Sheet 1 Filed Oct. 11, 1939 Lewis P M v A ter-neg:

By E. W,

F 1941. N. D. G. ROBERTSON EIAL 2,232,886

MELTING AND CASTING OF METALS Filed Oct... 11., 1959' Y z sheets-sh et'2 IV. D. 6'. Robe/tun and By 8 7* Q Aflqhneys v Patented Feb. 25,1941

netmcmn meme mun i [Nell DouIEiGorJonBobeI-tson, Bushey Heath,

' and Eric Crisp lcwis l'ntnemllondomlilnzlsnd, i

llfltn rlloMalnesiumllektron HmiteilmadolilEllzlend a-Brltlshcompgny' 21 v i iilicwefi amum;ims;seaum. 299,014 1 In Gre otBrlt ginoctoberzo,1938 g y l y b v 22141914 This invention relates to the fneltingilendj tie-:1

ing otmetals.

According to the inyentlon theiibbaratusfcom,

prises a. crucible adapted tocontain molten metal 5 and gas underpressure, and having adelivery,

pipe adapted to extendjb elow. I the level of {the molten metal, itsupper end beirigl outside the crucible for dellyery ot molten metal; 12,device containing gas, preferably inert to "the r'noltenfl metelandconnected by a. pipette tliejinterion of the crucible andl aylngrelatively movable walls and means for "moving said walls towards eachother tog'eneratethe .required gas pressure (without other means forsupplying ges Iunder gmay'fbe" dlsben'sed wlth altogether. The rvessel.rnaybe af crucible for normal @Ioundry. work or jrnay 'of tlie largetyr suitable wfor magnesium production or alloying purposes. Theexpelled metalf inay be received directly into a; ladle for v casting orinto a mould-tor. sand or permanent lfmould casting-tr may enterepressure chamber Q for injection into 'a 'mould ot'a. pressuredie-cest-;;10,, fing machine or directly "into the mould ot suchbut Inot ncesserily for t the" 6: sbrotecting the magnesium fromoxidatlonyaand a machine. i

v The deliveryplpe is preferably constentlyopen to the moltenmetafbeneath theupper surfacexi pressure) which is transmitted to thecrucible. thereofand is of such increaslngdlameterwith-9therebyyexpelling molten metal through the de vin tliecrucible fromltsupper end downwards livery pipe and forfmoving saigl walls apart toas tofpreve nt jafiiming should metalsbecorne so; :4 reduce saidpressure, thereby 'jstoppingtl out;" lidifledfthereln;andtOr'ender-removal o solidiflow offmetel; through thedeliverypipeandrel fied'metaran easy 'matterpf" 11m 1, y

turning the metal inthe delivery pipe to e, re; 1 In order thjt tliedboveoescrlbed iand otherx quiredwlevel there being noqoutlet, in the gafeatures of the inyention may' be more easilyle system during usethrough whlch any appre i understood afconstruotionaliorm of theinvent-t able lossof the gas couldmormelly occur llfh tion will nowbefdescribed- -by wayof examplew.

atm D B eoIZ-QEELS withinmthe vessel wlllbe sewith referenceito theaccompanying diegramlected according to the requlrements -of ;the mati cdra wings,- wherein. w H

metalconcerned. Ifmagnesiurn or amegnesium Figure '1, is*efvertialsectional e :of an base alloy; or analuminium base alloycontain appa ratus irlgde' n accordance withth invertingt a.proportiorrof magnesium isbeing treatedr tion; d f i i o theetm'ospherein,thepvessel may besulplourqdl- Figur e j2 illustretesfa modlflcationto be de- L oxideor hydrogen" or hydrogen,;.su1ph1de;orother rscribedfli w gases .inertdr' comparatively inert to magnesium; 5x A crucible3rnount ediira idrnag'ce 4 is formed or mixturesmof suchgrgases or air-an d;sulf)hur from iron, steel, or other suitable. matermr or p w yrbeivusedr rf p rcor th ixm e oy, of ve ted; dome-shape and withofitopen xalsrthe*atmosphererwill be-suitably chosen andvings therein exceptof coursl its open up e will ;.usually:=be-;inert' to the metal undertreatt end. The crucible is provided with an outwardly mentm ItT -is.yerywdesireble however;that; gases directed file getrounditsupperjend'or mouth which are appreciably soluble iinthe meltshouldq 1d Win a; s-tight not bewemployed. or (porosity 01313118 finalcastings 1 40 Xmay resu1t.+ The: ;gas employed, furthermor e, v may-betchosen with xa view towefiecting a.Jciev oxidationrof; themoltenmetahge. g. hydrogen or 11 carbon-monoxide: v i ,1; 11

Whenqtreating magnesium or alloys scontain ting i magnesium; the; metalmay bevflrst purified bywusuals fluxmethods or may beipulsfledbyefluxintroduced Jintoi, thet-g cruciblegit self, ,{If large Iscrap :x(suclr as :foundry; runners p,nd;;-; T sers ,;;o1 ingot istoibeintroduoed lntosthe crucible it m ay 1 .1 first treated: to 1 removesurfacer vimpuritiesr;

e. ig; 1 by n sendiablasting'; If rflux; is i to ghei introduced intothe crucible this maybe 'ofthe very,

fluidr'nature 'orl 10f :hormelly torvmore @than norf1;mallyv-irispissatedanature; ore awfiuidi-flux may 551F136 -used vflrstandithen insplssated later; but the The -inside p V a t y lie ee m diamter!" freeziee 6 m l here n rnet 1 if it snomas'ou an inch in diameterat its upper end, according I bottom of the crucible or may be higher toavoid picking up any sediment, and may conveniently be six inches indiameter at its lower end, and say to requirements. The lower end of thepipe is constantly open to receive molten metal. The inner surface ofthe-delivery pipe is unbroken by any valve device and presents acontinuous surface from its lower inlet end to its outlet or deliveryend. The openings I are large enough to permit withdrawal of thedelivery pipes therethrough.

Passing through the cover 6 is a gas tube IS. The gas in the crucibletends to escape when themetal charging opening is opened and thussubstantially prevents ingress of air. The gas tube is connected to achamber it having relatively movable walls, e. g. a bellows (as shown)or pistonand cylinder, which walls can be moved towards or away fromeach other by hand or power to produce negative, zero, or positivepressure within the crucible, variable at will. This chamber will notnecessarily require to be in communication with a supply of gas underpressure, and as shown receives gas through a pipe I! and nonreturnvalve It. In the example illustrated the bellows is contained in a metaljacket I! and the top plate 2! of the bellows carries an up wardlyextending toothed rack 2| with which a splined shaft 12 gears, thisshaft having a handle 23 whereby the operator can move the walls of thebellows towards each -other or apart for increasing or decreasing thepressure of gas in the crucible 'without loss of gas. The operator willapply a slight positive pressure to elect metal and will reduce thepressure to stop the flow and enable the level of metal to fall in thedelivery pipe. when the pressure in the bellows is below atmosphericpressure, the non-return valve situated in the bellows inlet pipe opensand inert gas or a mixture of sulphur dust and air. etc.. is drawn intothe bellows. Immediately the pressure rises above atmospheric thenon-return valve closes and pressure is built up in the crucible. Thepressure used for ejecting the metal preferably is less than say 5 lbs.per square inch and; may be only about lb. with very fiuid metal. Novalve or other means for permitting escape of the gas from the crucibleto the atmosphere is required since the gas in the chamber can be' usedcontinuously. A cock or blow off valve may be provided in the gas pipeit. This chamber may be connected to two or more such crucibles throughthe medium of a distributing cock if desired.

In employing the apparatus a charge of metal or alloy, such for exampleas magnesium, magnesium alloy, aluminium alloy or copper alloy, isplaced within the crucible through the charging door melted, cleaned andif necessary refined, and the door is closed. The dies or moulds may bearranged upon a platform or secured in position in any convenient mannerwith their "feeders or runners" adjacent to the delivery pipe. Pressuremay then be increased in the chamber to raise the internal pressure to aconvenient amount to expel the metal into the dies or moulds.

In the modification shown in Figure 2 the outlet end 26 of the deliverypipe is shaped to receive a nozzle 26 on the bottom of a ladle 28 sothat no metal will be left to solidify in this open ing. For thispurpose the ladle may have such a nozzle at the lower part thereofcorresponding in shape to the shape of the outlet opening. The interiorof'this nozzle may also be of frustoaasasee conical shape to receive aball on the lower end of a vertical rod. The ball serves as a valve toprevent-egress of metal but will be pushed upwardly by the metalreceived from the crucible. The rod may carry a circular or dished plateto prevent the incoming metal from spurting too far upwardly. The ladlemay be lagged and provided with a cover plate. The ladle may be placedin a supporting frame when not in use. These details of the ladle arenot illustrated as they are well known in the foundry industry.

The crucible may be maintained in the furnace for long periods, thusreducing heat losses, and may be fitted with a pyrometer, safety valve,and other desired parts. Two or more crucibles may be used so that asupply of metal can be arranged always to be available in at least oneof them.

We claim:

1. An apparatus comprising a crucible adapted to contain molten metaland gas-under pressure, a delivery conduit adapted to extend below thelevel of the molten metal and having its upper end outside the cruciblefor the delivery of molten metal, a device containing gas and havingrelatively movable walls, a pipe connecting such device to the interiorof the crucible and constructed to enable the flow of gas between thedevice and the crucible to occur in either direc-- tion along the pipeat any moment, the said device, pipe and crucible forming a gas system,means for moving such walls towards each other to generate the requiredgas pressure which is transmitted along said pipe to the cruciblethereby expelling the molten metal through the delivery conduit and formoving said walls apart whereby said pressure is reduced therebystopping the outflow of metal through the delivery conduit and returningthe metal in the delivery conduit to a required level, there being nooutlet in the gas .systeni during use through which any appreciable lossof the gas could normally occur, an inlet for gas to the said system,and an automatically operating return valve controlling said inlet andpermitting gas to enter said system if the gas pressure in said systemfalls below a predetermined degree.

2. An apparatus comprising a crucible adapted to contain molten metaland gas under pressure, a delivery conduit comprising a pipe adapted toextend below the level of the molten metal and having its upper endoutside of the crucible for delivery of moltenmetal, the conduit beingconstantly open to the molten metal beneath the upper surface thereofand of such increasing diameter within the crucible from its upper enddownwards as to enable solidification of the metal therein to beavoided, means whereby said pipe i'snormally held in position inrelation to the crucible and whereby the delivery pipe can bereadilyremoved from the crucible for cleaning, a device containing gasand having relatively movable walls, a pipe connecting such device tothe interior of the crucible and constructed to enable the fiow of gasbetween the device and the crucible to occur in either direction alongthe pipe at any moment, the said device, pipe and crucible forming a gassystem, hand operable means for moving such walls by mechanicalconnections towards each other to'generate the required gas pressurewhichis transmitted along said pipe to the crucible thereby expellingthe molten metal through the delivery conduit and for moving said wallsapart whereby said pressure is reduced thereby' stopping the outflow ofmetal through the delivery conduit and retumaasaaso ,3

ing the metal in the delivery conduit to a required mitting gas to entersaid. system it the gas pres level, there being no outlet in the gassystem .sure in said system falls below a predetermined during usethrough which any appreciable loss degree. of the gas could normallyoccur, an inlet for gas 5 tothe said system, and an automaticallyoperat- NEIL DOUGLAS GORDON ROBERTSON. 5

flng return valve controlling said inlet and per-; ERIC CRISP LEWIS.

